1. Field of the Invention
The present invention relates to a high frequency relay.
2. Disclosure of the Prior Art
In the past, high frequency relays have been used to switch high frequency signals. For example, Japanese Patent Early Publication [KOKAI] No. 1-274333 discloses that a high frequency relay comprises a base, on which fixed contacts of gold-plated pins are mounted, a card having contact springs, a shield case having earth terminals manufactured by working a sheet metal, an electromagnet for moving the contact springs to open and close a pair of the fixed contacts by the contact spring, and a shield cover.
However, in this kind of high frequency relay, there are problems that variations in high frequency characteristic of the high frequency relay such as such as insertion loss, isolation loss and V.S.W.R. (reflection) occurs due to errors in working and assembling the relay components. On the other hand, when working and assembling the relay components with high accuracy, there is another problem of increasing the production cost of the high frequency relay in a large amount. In particular, as the relay becomes smaller in size, there is a limitation of working and assembling the relay components with high accuracy.
Therefore, a primary object of the present invention is to provide a high frequency relay capable of improving electromagnetic shield effect for preventing signal leakage and minimizing variations in high frequency characteristic resulting from steps of working and assembly the relay components.
That is, in the high frequency relay comprising a contact base block having at least one pair of fixed contacts, at least one contact member with a movable contact, and an electromagnet for moving the contact member to open and close the pair of fixed contacts by the movable contact, the contact base block comprises a base having at least one pair of projections on its top surface, which is an injection-molded article of an electrical insulating material; first metal films formed as the fixed contacts on top surfaces of the projections; second metal films formed as connection terminals for outside devices on the base, each of which corresponds to one of the first metal films; connecting means for making an electrical connection between each of the first metal films and the corresponding second metal film; and a third metal film at least formed on the top surface of the base to provide electrical isolation from the first and second metal films, which works as electromagnetic shield means.
By the way, to stabilize the high frequency characteristic of the high frequency relay, it is important to keep the assembly accuracy of relay components constant. In particular, it is required to accurately determine a distance between each of the fixed contacts and the corresponding connection terminal. In the past, when the relay components including the fixed contacts and the connection terminals are provided as separate parts, it is required to work and assemble each of the relay components with high accuracy, so that there is another problem of increasing the production cost.
In the present invention, since the first, second and the third metal films, which respectively function as the fixed contacts, connection terminals, and the electromagnetic shield means for preventing the leakage of the high frequency signals, are integrally formed on the injection-molded base, it is possible to readily and accurately control the distance between each of the fixed contacts and the corresponding connection terminal, and sharply reduce the total number of the relay components. According to these advantages, the present invention can stably provide the high frequency relay having a constant high frequency characteristic. In particular, as the high frequency relay becomes smaller in size, the present invention becomes to be more effective. Moreover, since the first metal films that are the fixed contacts are formed on the top surfaces of the projections, the movable contact can open and close the fixed contacts with reliability without contacting the third metal film.
In a preferred embodiment of the present invention, the high frequency relay further comprises a contact sub block for movably supporting the contact member, which comprises a subbase that is an injection-molded article of an electrical insulating material, and a fourth metal film formed on a surface of the subbase in a face to face relation with the top surface of the base when the contact sub block is mounted on the contact base block, so that the pair of fixed contacts are opened and closed by the movable contact in an electromagnetic shield space surrounded by the third and fourth metal films.
It is preferred that each of the second metal films is formed on a bottom surface of the base at a position opposed to the corresponding one of the first metal films. In this case, it is preferred that the connecting means is through holes each having a conductive layer on its inner surface, each of which is formed in the base to electrically connect one of the first metal films with the corresponding second metal film in the shortest distance.
It is further preferred that each of the projections has a first projection jutting from the top surface of the base and a second projection jutting from the first projection, and wherein each of the first metal films is formed on a top of the second projection and the third metal film is formed on side surfaces of the first projections. In addition, it is preferred that each of the projections has a rounded top, on which the first metal film is formed.
In addition, it is preferred that the high frequency relay comprises a first contact set of a first pair of fixed contacts and a first contact member used to switch a high frequency signal and a second contact set of a second pair of fixed contacts and a second contact member used to switch another high frequency signal, and wherein a shield wall for isolating the first contact set from the second contact set is integrally-molded with at least one of the base and the subbase.
In addition, it is preferred that the high frequency relay comprises a coil block for housing the electromagnet comprises an armature disposed between the contact member and the electromagnet and driven by energizing the electromagnet, and a motion of the armature is transferred to the contact member through a first spring member held by a spring holding portion integrally molded with the subbase.
Moreover, it is preferred that a coil block supporting portion for supporting the coil block and the spring holding portion are provided on a surface opposed to the surface having the fourth metal film of the subbase, and the contact member is attached to a through hole formed in the subbase with a second spring member such that the contact member receives a spring bias of the second spring member in a direction of spacing the movable contact from the fixed contacts, and the contact member can be moved against the spring bias of the second spring member by the first spring member pushed by the armature to close the fixed contacts by the movable contact.
It is also preferred that the high frequency relay comprises fifth metal films formed as coil electrodes for supplying electric power to the electromagnet on the base so as to provide electrical isolation from the first, second and third metal films.
Another object of the present invention is to provide a high frequency relay having the following structure. That is, in the high frequency relay comprising a contact base block having at least one pair of fixed contacts, at least one contact member with a movable contact, a contact sub block for movably supporting the contact member, and an electromagnet for moving the contact member to open and close the pair of fixed contacts by the movable contact, the contact base block comprises a base that is an injection-molded article of an electrical insulating material; first metal films formed as the fixed contacts on a top surface of the base; second metal films formed as connection terminals for outside devices on the base, each of which corresponds to one of the first metal films; connecting means for making an electrical connection between each of the first metal films and the corresponding second metal film; and a third metal film at least formed on the top surface of the base to provide electrical isolation from the first and second metal films, which works as electromagnetic shield means. In addition, the contact sub block comprises a subbase that is an injection-molded article of an electrical insulating material, and a fourth metal film formed on a surface of the subbase in a face to face relation with the top surface of the base when the contact sub block is mounted on the contact base block, so that the pair of fixed contacts are opened and closed by the movable contact in an electromagnetic shield space surrounded by the third and fourth metal films.
In the present invention, since the first, second and the third metal films, which respectively function as the fixed contacts, connection terminals, and the electromagnetic shield means for preventing the leakage of the high frequency signals, are integrally formed on the injection-molded base, and the fourth metal film is integrally formed as the electromagnetic shield means on the injection-molded subbase, there is an advantage that the electromagnetic shield space having a remarkable effect of preventing the signal leakage can be stably obtained in the high frequency relay by the third and fourth metal films even when the high frequency relay is small-sized.
These and still other objects and advantages will become apparent from the following detailed description of the invention.